Index | Examples | Syntax Device Drivers | Section 2


HIMEM tests the reliability of your extended memory The MS-DOS 6.22 version of HIMEM.SYS includes a special safety feature: it tests your computer's extended memory each time your computer starts. HIMEM tests the memory by writing and reading data to each memory address and checking for differences in the data. If the data HIMEM reads from an address differs from the data it just wrote to that address, then the memory at that address is unreliable. Unreliable memory can cause system instability or loss of data. HIMEM's memory test is more thorough than the standard power-up memory test performed by most computers. If HIMEM detects unreliable memory, it displays the following message and does not load: ERROR: HIMEM.SYS has detected unreliable extended memory at address XXXXXXXXh. If you receive this message, you should have your computer's memory checked by a qualified computer hardware technician. Although you can disable the memory test and load HIMEM by using the /TESTMEM:OFF switch, it's not advisable to do so until you have had the memory checked by a technician. Default memory allocation Only one program at a time can use the high memory area (HMA). If you omit the /HMAMIN=m switch (or set it to 0), HIMEM reserves the HMA for the first program that requests it and that meets the memory requirements set by the /HMAMIN=m switch. To ensure the most efficient use of your system's high memory area, set /HMAMIN=m to the amount of memory required by the program that uses the most HMA memory. Loading MS-DOS into the high memory area HIMEM or another XMS driver must be loaded in order to load MS-DOS into the high memory area (HMA). You load MS-DOS into the HMA by using the DOS=HIGH command in your CONFIG.SYS file. (The DOS=HIGH command can appear anywhere in the CONFIG.SYS file.)
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